An electro-mechanical actuator for an aircraft brake assembly often incorporates a ball screw that rotates to drive a ball nut piston in an axial direction. The ball nut piston may have an endcap, and a puck may be inserted in the endcap. The puck may contact a brake disk to exert a braking force. The puck may be retained in the endcap with a retention spring. However, in some cases, vibrations or ice build-up around the puck may cause the puck to fall out the endcap. This may cause significant damage to a brake system and decrease the braking ability of the aircraft, as well as create foreign object damage to aircraft on a runway which may contact or ingest the puck.